Comedian Ronnie Corbett was rushed to hospital suffering from chest pains, his wife said.
The 83-year-old underwent tests for several days last week before being discharged in time to attend the memorial of close friend Sir David Frost.
Ronnie fell ill at his home near Croydon in south London last Sunday when he suffered chest and stomach pains and felt nauseous, the Sunday Mirror said.
He was taken to the Princess Royal University Hospital in Bromley but doctors were unable to diagnose the problem.
His wife Anne told the newspaper: "We didn't know what was wrong. He was feeling sick in his stomach and he wasn't well. The hospital ran lots of tests, he was in there for several days."
She said the illness could spell the end of his career on television, saying: "He won't be doing any more TV - he's 83. He won't be like Bruce Forsyth."
Ronnie was later well enough to read a prayer at the Westminster Abbey memorial service for Sir David on Thursday.
It was on Sir David's 1960s show The Frost Report that Ronnie first rose to fame, through which he met fellow comedian Ronnie Barker.
The pair went on to forge one of Britain's best-loved TV partnerships in their long-running The Two Ronnies sketch show.
Anne told the Sunday Mirror he had been adamant he wanted to be at Sir David's memorial, saying: "It was such an emotional day and Ronnie was determined to be there."
She added: "It was wonderful and very emotional. Ronnie wouldn't have gone if he hadn't been feeling okay then."
Ronnie has suffered health scares before.
He has had a knee operation and collapsed on New Year's Day in 2012 during a family meal, and was put on medication after being diagnosed with low blood pressure.
His doctor also sent him to the Priory clinic because of fears over his health, but Ronnie later said his visit lasted just 10 minutes, when a psychiatrist told him he was fine.